German patent application DE 102 50 050 A1 discloses that the efficiency of the reduction catalyst can be increased if combustion heat of an internal combustion engine is utilized.
Furthermore, German patent application 10 2008 051 496 A1 indicates that a high exhaust-gas temperature is beneficial for the operation of the reduction catalyst.
German patent application DE 103 23 607 A1 describes a device that is used for the exhaust-gas purification of an internal combustion engine and that has an oxidation catalyst, a particle filter and a reduction catalyst. The reduction catalyst is combined into one structural unit together with the particle filter.